Abstract
BackgroundObesity is a risk factor for cancer incidence and survival, but data on patterns of weight change in cancer survivors are scarce and few stratify by pre-diagnosis weight status. In two population-based cohorts of older adults, we examined weight change in cancer survivors and cancer-free controls in relation to baseline weight status.MethodsIn the English Longitudinal Study of Ageing (ELSA) and the Health and Retirement Study (HRS), we identified participants diagnosed with cancer who had pre- and post-diagnosis BMI data (ELSA n = 264; HRS n = 2553), and cancer-free controls (ELSA n = 1538; HRS n = 4946). Repeated-measures ANOVAs tested three-way interactions by group (cancer/control), time (pre-/post-diagnosis), and pre-diagnosis weight status (normal-weight/overweight/obese).ResultsMean BMI change was -0.07 (SD = 2.22) in cancer survivors vs. +0.14 (SD = 1.11) in cancer-free controls in ELSA, and -0.20 (SD = 2.84) vs. +0.11 (SD = 0.93) respectively in HRS. Three-way interactions were significant in both cohorts (ELSA p = .015; HRS p < .001). In ELSA, mean BMI change in normal-weight cancer survivors was +0.19 (SD = 1.53) compared with -0.33 (SD = 3.04) in obese survivors. In ELSA controls, the respective figures were +0.09 (SD = 0.81) and +0.16 (SD = 1.50). In HRS, mean change in normal-weight cancer survivors was +0.07 (SD = 2.30) compared with -0.72 (SD = 3.53) in obese survivors. In HRS controls, the respective figures were +0.003 (SD = 0.66) and +0.27 (SD = 1.27).ConclusionOver a four-year period, in two cohorts of older adults, cancer survivors lost weight relative to cancer-free controls. However, cancer survivors who were obese pre-diagnosis were more likely to lose weight than healthy-weight survivors or obese adults without a cancer diagnosis. Whether this was due to differences in clinical status or deliberate lifestyle change triggered by the cancer diagnosis is not known. Further research is needed to establish why weight loss occurs more frequently in cancer survivors who were obese at diagnosis, and whether this has favourable effects on mortality.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2407-14-926) contains supplementary material, which is available to authorized users.
Highlights
Obesity is a risk factor for cancer incidence and survival, but data on patterns of weight change in cancer survivors are scarce and few stratify by pre-diagnosis weight status
Two exceptions are the Norwegian Women and Cancer study, which found BMI change over a six-year period from pre- to post-diagnosis did not differ between women who developed cancer and those who remained cancer-free [16], and the Danish Diet, Cancer and Health cohort, where women who were diagnosed with breast cancer had a BMI change similar to those who remained cancer-free [17], men in the same cohort who were diagnosed with cancer experienced a reduction in BMI relative to controls [18]
We examined the three-way interaction between group, time, and pre-diagnosis weight status to test the hypothesis that the BMI change would vary by weight status
Summary
Obesity is a risk factor for cancer incidence and survival, but data on patterns of weight change in cancer survivors are scarce and few stratify by pre-diagnosis weight status. Two exceptions are the Norwegian Women and Cancer study, which found BMI change over a six-year period from pre- to post-diagnosis did not differ between women who developed cancer (breast or colorectal) and those who remained cancer-free [16], and the Danish Diet, Cancer and Health cohort, where women who were diagnosed with breast cancer had a BMI change similar to those who remained cancer-free [17], men in the same cohort who were diagnosed with cancer experienced a reduction in BMI relative to controls [18] While these studies offer valuable insight into weight change following a cancer diagnosis, overall BMI changes may disguise differential patterns of change by weight status. A cancer diagnosis could act as a ‘teachable moment’ [20]; promoting healthy lifestyle changes and resulting in more effective weight control; one previous study found that patients with a higher BMI were at lower risk of post-diagnosis weight gain [19]
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